Prestressed concrete structure, reinforcing member used for the prestressed concrete molded articles, and sheet member used for the reinforcing member

ABSTRACT

A prestressed concrete structure comprising an elongated concrete molded article having a pair of side surfaces opposed to each other, a plurality of tensile members laterally extending through the concrete molded article to be secured at each end to the side surfaces of the concrete molded article in a tensioned state and imparting a compressive load to the concrete molded article, side guards arranged along both side surfaces of the concrete molded article so as to cover the ends of the tensile members, and reinforcing members arranged on the side surfaces of the side guards in order to prevent the broken tensile members from protruding beyond the side surfaces thereof breaking through the side guards when the tensile members in the tensioned state are broken. The reinforcing members stretch little in the longitudinal direction but easily stretch in the transverse direction on the side surfaces of the side guards, and when pushed from the inside by the ends of the tensile members that protrude as a result of breakage, the peeling of the reinforcing members spreads out in the longitudinal direction of the concrete molded article on the side surfaces of the side guards but spreads out little in the transverse direction.

This application is a continuation of PCT application No. PCT/JP98/03861filed on Aug. 28, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a prestressed concrete structure. Morespecifically, the invention relates to a prestressed concrete structurewhich, when PC steel members tightening a concrete molded article ortightening a plurality of concrete molded articles are broken, preventsthe broken PC steel members from protruding or projecting outward beyondthe side portions of the prestressed concrete structure.

2. Description of the Related Art

Prestressed concrete has heretofore been widely known. Prestressedconcrete is a technology for enhancing the tensile load characteristicsof the concrete by imparting a compressive load prior to the use, and isgenerally used for large concrete structures such as bridge structures.The compressive load can be imparted to the prestressed concrete invarious ways. In a large concrete structure, the compressive load isoften imparted relying on a pre-tension method, a post-tension method ora combination of the pre-tension method and the post-tension method.

In a large concrete structure and, particularly, the one adapted to thebridge structures, a plurality of tension members constituted by PCsteel rods or PC steel wires that extend in a horizontally transversedirection perpendicular to the longitudinal direction of the bridges,are arranged in parallel in the horizontally longitudinal direction, sothat a plurality of neighboring concrete molded articles are fastenedtogether by these tension members, and a large tension is given to thetension members to tighten the concrete molded articles, in order toimpart compressive load in the transverse direction to each of theconcrete molded articles. In the thus formed concrete structure, in casea tension member to which a large tensile force is imparted breaks dueto some cause, the broken tensile member protrudes or projects outwardbeyond the side portion of the concrete structure.

In order to solve this problem according to, for example, JapanesePatent No. 2742675, a reinforcing sheet of carbon fibers, aramid fibersor a combination thereof is adhered onto the axes of the PC steelmembers on the side surface of the prestressed concrete structure. Inthis reinforcing sheet, the warps and wefts are composed of fibers ofthe same material. When hit by the broken PC steel member, therefore,the reinforcing sheet peels roughly uniformly off the side surface ofthe prestressed concrete structure. When the reinforcing sheet is peeledup to the edges of the prestressed concrete structure, therefore, thereresults a conspicuous decrease in the adhesion strength of thereinforcing sheet on the side surface of the prestressed concretestructure. As described above, the reinforcing sheet is roughlyuniformly peeled off the side surface of the prestressed concretestructure. When the prestressed concrete structure is a long one such asa bridge structure and has a side surface of an elongated shape, i.e.,when the aspect ratio is relatively great, the peeling, which proceedsin a direction in parallel with the short side, quickly arrives at theedge of the prestressed concrete structure resulting in a remarkabledrop in the adhesion strength of the reinforcing sheet.

The present invention was accomplished in order to solve this problem,and its object is to provide a prestressed concrete structure which,when the PC steel members used in the prestressed concrete structure arebroken, prevents the broken PC steel members from protruding orprojecting outward beyond the side portions of the prestressed concretestructure.

Another object of the present invention is to provide a fiber-reinforcedresin composite material used for preventing the broken PC steel membersfrom protruding or projecting outward beyond the side portions of theprestressed concrete structure.

A further object of the present invention is to provide a sheet memberused for preventing the broken PC steel materials from protruding orprojecting outward beyond the side portions of the prestressed concretestructure.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a prestressedconcrete structure comprising:

a long concrete molded article having a pair of side surfaces opposed toeach other;

a plurality of tensile members penetrating and stretching inside theconcrete molded article from one of the pair of the surfaces toward theother the surface in a transverse direction, secured at their both endsto the the surfaces of the concrete molded article in a tensioned state,and are imparting a compressive load to the concrete molded article;

a pair of side guards arranged along both side surfaces of the concretemolded article so as to cover the ends of the tensile members; and

reinforcing members arranged on the side surfaces of the pair of theguards in order to prevent the broken tensile members from protrudingbeyond the side surfaces thereof breaking through the side guards whenthe tensile members in the tensioned state are broken; wherein

the reinforcing members stretch little in the longitudinal direction ofthe side surfaces of the side guards but easily stretch in thetransverse direction on the the surfaces of the side guards and, whenpushed from the inside by the ends of the tensile members that protrudeas a result of breakage, the peeling of the reinforcing members easilyspreads out in the longitudinal direction of the side surfaces of theside guards but spreads out little in the transverse direction on thethe surfaces of the side guides.

The tensile member that is broken no longer imparts a tensile force.Therefore, a large thrust acts upon the broken tensile member in theaxial direction thereof. Due to the thrust, the broken tensile membermoves in the axial direction. The magnitude of thrust acting on thetensile member at breakage varies depending upon the conditions such asthe length of the tensile member that is broken, magnitude of tensionacting on the tensile member at breakage, rate of progress leading tobreakage, material of the tensile member, and the like. When the tensilemember is a PC steel rod, in particular, it has been known that a largethrust acts. When the thrust is great, the broken tensile members oftenprotrude beyond the side surfaces of the side guards.

According to the present invention, the tensile members that protrudepenetrating through the side guard come into collision with thereinforcing member provided on the side surface of the side guard. Thereinforcing member is peeled off the side surface of the side guardwhile being stretched, thereby to effectively absorb the kinetic energyof the tensile members that are broken.

In general, as the peeling of the reinforcing member spreads out andreaches the upper and lower edges on the side surface of the side guard,the bonding force of the reinforcing member on the side surface of theside guard greatly drops at that portion resulting in a sharp decreasein the ability for absorbing the kinetic energy of the tensile membersthat are broken. According to the present invention, the reinforcingmember stretches little in the longitudinal direction but easilystretches in the transverse direction on the side surface of the sideguard. Therefore, peeling of the reinforcing member spreads out in thelongitudinal direction on the surface of the side guard but hardlyspreads out in the transverse direction to alleviate the above-mentionedproblem.

Preferably, furthermore, the reinforcing member includes warps thatextend in the longitudinal direction on the side surfaces of said sideguards, wefts that extend in the transverse direction, and a resinmaterial for bonding said warps and said wefts, said warps having atensile modulus of from 5000 to 18000 kgf/mm² and said wefts having atensile modulus of from 300 to 4500 kgf/mm².

The warps having a large tensile modulus stretch little. Therefore, thereinforcing members stretch little in the longitudinal direction on theside surfaces of the side guards and are easily peeled off the sidesurfaces of the side guards. Upon decreasing the tensile modulus of thewefts, the reinforcing member is allowed to easily stretch in thetransverse direction on the side surfaces of the side guards and arehardly peeled off.

A further feature of the present invention is to provide afiber-reinforced resin composite material comprising a woven fabric ofaramid fibers and non-aramid fibers, and a resin for bonding said wovenfabric, said woven fabric having a tensile modulus of from 3000 to 15000kgf/mm² in the direction of aramid fibers and a tensile modulus of from150 to 3000 kgf/mm² in the direction of non-aramid fibers.

A still further feature of the present invention is to provide a sheetmember containing a woven fabric of aramid fibers and non-aramid fibers,said woven fabric having a tensile modulus of from 3000 to 15000 kgf/mm²in the direction of aramid fibers and a tensile modulus of from 150 to3000 kgf/mm² in the direction of non-aramid fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating, on an enlarged scale, a majorportion of a prestressed concrete structure according to the presentinvention;

FIG. 2 is a front view illustrating, partly in cross section, areinforcing member;

FIG. 3 is a perspective view of the prestressed concrete structure onthe bridge piers; and

FIG. 4 is a perspective view of a side portion of the prestressedconcrete structure for illustrating another embodiment of thereinforcing member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will now be described withreference to the accompanying drawings dealing with a prestressedconcrete bridge structure. The prestressed concrete bridge structure isformed by bonding and fastening a plurality of concrete molded articlesarranged neighboring one another by using tensile members (hereinaftersimply referred to as PC steel members) constituted by a plurality of PCsteel rods or PC steel wires.

Referring to FIG. 3, a large prestressed concrete structure 10 isinstalled on a plurality of bridge piers 1 erected maintaining apredetermined distance in the longitudinal direction indicated by anarrow “a”. The prestressed concrete structure 10 comprises a pluralityof long concrete molded articles 11 having a nearly T-shape in crosssection, the concrete molded articles 11 being coupled and tightenedtogether by a plurality of PC steel members 12 that are arranged toextend in the horizontally transverse direction. In FIG. 3, the PC steelmembers 12 are arranged in one layer in the horizontal direction but maybe arranged in a plurality of layers of two or more layers, as a matterof course.

Referring to FIG. 1, each concrete molded article 11 has a hollow tubeor a sleeve 13 that penetrates through and extends in the transversedirection. The sleeve 13 can be arranged in advance in a molding flask(not shown) before the molding flask is filled with a concrete. The PCsteel member 12 is passed through the sleeve 13 and is then tightened byusing a tension-imparting device such as a jack. Nuts 15 screwed ontoboth ends of the PC steel member 12 are tightened, and both ends of thePC steel member 12 are fixed to the side surfaces 16 of the concretemolded article 11 located on the outermost sides via a washer 14. Acompressive load is imparted to the concrete molded article 11 due tothe tension acting on the PC steel member 12. A gap between the PC steelmember 12 and the sleeve 13 may be filled with a mortar or a paste toprevent the corrosion of the PC steel member 12.

The ends of the PC steel member 12 protrude beyond both side surfaces ofthe prestressed concrete structure 10, i.e., protrude beyond the sidesurfaces 16 of the concrete molded articles located on the outermostsides among a plurality of concrete molded articles arranged inparallel. Besides, as shown in FIG. 1, ground covers or side guides 17made of a concrete or a mortar and having an L-shape in cross section,have heretofore been provided for the outer side surfaces 16. The sideguards 17 prevent the vehicles from falling off the bridge and furtherprevent the PC steel member from protruding or projecting beyond theside portions of the prestressed concrete structure 10 in case the PCsteel member 12 on which the tension is exerted is broken. According tothe constitution of the prior art, however, the PC steel member 12 thatis broken may project outward breaking through the side guard 17depending upon the conditions at the time of breakage. To completelyprevent the broken PC steel member from breaking through the side guard17, it becomes necessary to form very strong side guards 17 which arelarge in size, driving up the cost of construction.

In a preferred embodiment of the present invention as shown in FIGS. 1and 3, a reinforcing member 20 is stuck, using an adhesive agent, to theside surface 17 a of the side guard 17 to reinforce the side surface 17a of the side guard 17 with the reinforcing member 20. The reinforcingmember 20 includes a covering member 21 and a backing member 22. Thebacking member 22 is provided between the covering member 21 and theside surface 17 a of the side guard 17, and is arranged on a straightline relative to the PC steel member 12. As shown in FIG. 3, thereinforcing member 20 may have roughly the same length as the overalllength of the side guard 17 in the longitudinal direction but may bedivided to facilitate the transportation and the mounting operation.

Desirably, the backing member 22 has a side surface smaller than thearea of the side surface 17 a of the side guard 17. When the area of thebacking member 22 is nearly equal to the area of the side surface 17 aof the side guard 17, the reinforcing member 20 is little stretched anddeformed when the PC steel member that is broken comes into collisionwith the backing member 22, and the covering member 21 is easily peeledoff the side guard 17. When the area of the backing member 22 is verymuch smaller than the area of the covering member 21, stress isconcentrated in the reinforcing member 20 when the PC steel member comesinto collision with the backing member 22, and the PC steel member mayeasily protrude by breaking through the reinforcing member 20.Desirably, the area of the backing member 22 is one-tenth to one-halfthe area of the side surface 17 a of the side guard 17.

Referring to FIG. 1, the covering member 21 is formed of afiber-reinforced resin composite material (FRP) obtained by bonding areinforcing fiber material 31 with a resin layer 32. The reinforcingfiber material 31 may be formed of a sheet member of a single layer or aplurality of layers of a woven fabric. The woven fabric includes warps41 of yarns containing aramid fibers and extending in the longitudinaldirection of the side surface 17 a of the side guard 17 indicated by anarrow “a” in FIG. 2, and wefts 42 of yarns containing non-aramid fibersand extending in the transverse direction of the side surface 17 a ofthe side guard 17 indicated by an arrow “b” in FIG. 2. Hereinafter, thetransverse direction is a vertical direction with respect to thelongitudinal direction of the side surface 17 a of the side guard 17.

The material of the resin layer 32 for bonding the reinforcing fibermaterial 31 is desirably selected from the group consisting of an epoxyresin, an urethane resin, an acrylic resin and an ester resin. The mostdesired material is the epoxy resin.

The wefts 42 have a tensile modulus smaller than that of the warps.Therefore, the wefts easily stretch compared with the warps 41. If thebroken PC steel member 12 protrudes by breaking through the side guard17 and collides with the backing member 22, the covering member 21 ispushed from the inside. The covering member 21 stretches little in thedirection of arrow “a” in FIG. 3, i.e., stretches little in thelongitudinal direction of the concrete molded article 11 or of the sideguard 17, but stretches in the vertical direction “b”. Therefore, thepeeling of the reinforcing member 20 from the side surface 17 a of theside guard 17 spreads out in the longitudinal direction a but hardlyspreads out in the vertical direction “b” perpendicular thereto.Therefore, the region of the reinforcing member 20 peeled off the sidesurface 17 a of the side guard 17 describes a generally elliptic shapehaving a long diameter in the longitudinal direction of the side surface17 a of the side guard 17.

On the other hand, when a material having a large tensile modulus isused for the warps and the wefts, the peeling spreads out similarly inthe longitudinal direction a and in the vertical direction “b”. When thepeeling of the reinforcing member 20 reaches the upper and lower edgesof the side surface of the side guard 17, the bonding force of thereinforcing member 20 to the side surface 17 a of the side guard 17conspicuously decreases at that portion and becomes no longer capable ofabsorbing the kinetic energy of the broken PC steel member thatprotrudes. According to the embodiment of the invention, the reinforcingmember 20 easily spreads out in the longitudinal direction “a” buthardly spreads out in the vertical direction “b” i.e., the reinforcingmember 20 peels off describing an elliptical shape having a longdiameter in the longitudinal direction “a” in order to alleviate theabove-mentioned problem. Accordingly, the reinforcing member 20 becomescapable of absorbing larger kinetic energy of the broken PC steelmember.

As a material having such properties, the warps 41 may comprise theyarns containing 100% by weight of aramid fibers or may comprise blendedyarns containing not less than 50% by weight of aramid fibers. Or, thewarps 41 may comprise the yarns of aramid fibers and the yarns of othermaterials arranged alternatingly. The wefts 42 may comprise the yarnscontaining non-aramid fibers of an organic material. If described indetail, the non-aramid fibers can be selected from the group consistingof polyester fibers, vinylon fibers and polyamide fibers. Mostdesirably, the nylon fibers are used.

The reinforcing fiber material 31 is not limited to the biaxially wovenfabric shown in FIG. 2 but may be a multi-axially woven fabric of threeor more axes.

Desirably, furthermore, the reinforcing fiber material 31 has thefollowing properties A and B of the woven fabric:

Property A: tensile modulus is from 150 to 15000 kgf/mm²,

Property B: tensile toughness is from 400 to 4000 kgf %/mm².

It is further desired to possess the property C.

Property C: tensile strength is from 50 to 350 kgf/mm².

The above-mentioned properties are the values per a sectional area ofthe fibers in the fiber-reinforced resin composite material, and thetensile toughness is a product of the stress and the elongation atbreakage, and the tensile strength is a stress at breakage. Describedbelow are the conditions of the tensile testing machine for measuringthe tensile modulus, tensile strength and elongation.

a) Transverse direction of the test piece (direction of warps):

Width of test piece: 12.5 mm

Kind of chuck: wedge

Distance of gripping: 100 mm

Method of detecting the elongation: strain gauge

Tension speed: 2 mm/min.

How to find the tensile modulus: Gradient of a straight line over arange of 40 to 60% of stress at breakage on a stress—elongation curve.

b) Longitudinal direction the test piece (direction of wefts):

Width of test piece: 12.5 mm

Kind of chuck: wedge

Distance of gripping: 100 mm

Method of detecting the elongation: tension tester

Tension speed: 50 mm/min.

How to find the tensile modulus: Gradient of a straight line over arange of 40 to 60% of stress at breakage on a stress—elongation curve.

The above-mentioned woven fabric has a desired tensile modulus over arange of from 150 to 15000 kgf/mm² and, more preferably, over a range offrom 200 to 10000 kgf/mm². When the tensile modulus is smaller than 150kgf/mm², a local elongation becomes conspicuous, and thefiber-reinforced resin composite material is broken through due to theconcentration of stress. When the tensile modulus exceeds 15000 kgf/mm²,on the other hand, the kinetic energy of the PC steel member that isbroken is not absorbed, and the fiber-reinforced resin compositematerial easily peels off the side surface of the side guard. Ifdescribed in further detail, the woven fabric desirably has a tensilemodulus of from 3000 to 15000 kgf/mm² in the direction of warps and hasa tensile modulus of from 150 to 3000 kgf/mm² in the direction of wefts.

The woven fabric has a desired tensile toughness over a range of from400 to 4000 kgf %/mm² and, more preferably, over a range of from 750 to3500 kgf %/mm. When the tensile toughness is smaller than 400 kgf %/mm²,the kinetic energy is not absorbed, and the fiber-reinforced resincomposite material is broken through by the PC steel member that isbroken. When the tensile toughness exceeds 4000 kgf %/mm², on the otherhand, the material fails to exhibit the tensile modulus over theabove-mentioned desired range, and the kinetic energy is not absorbed.If described in further detail, the woven fabric has a tensile toughnessof from 500 to 2000 kgf %/mm² in the direction of warps and has atensile toughness of from 400 to 4000 kgf %/mm² in the direction ofwefts.

The woven fabric has a desirable tensile strength over a range of from50 to 350 kgf/mm² and, more preferably, over a range of from 70 to 300kgf/mm². When the tensile strength is smaller than 50 kgf/mm², thekinetic energy is hardly absorbed, and the fiber-reinforced resincomposite material is broken through by the PC steel member that isbroken. When the tensile strength exceeds 350 kgf/mm², on the otherhand, the material fails to exhibit the tensile modulus over theabove-mentioned desired range. Therefore, the kinetic energy is notabsorbed, and the fiber-reinforced resin composite material easily peelsoff the side surface of the side guard. If further described in detail,the woven fabric has a tensile strength of from 200 to 350 kgf/mm² inthe direction of warps and a tensile strength of from 50 to 150 kgf/mm²in the direction of wefts.

The reinforcing fiber material 31 may not be the woven fabric shown inFIG. 2 but may be the one obtained, as shown in FIG. 4, by separatelysticking the warps 41′ and the wefts 42′ on the side surface 17 a of theside guard 17 in the longitudinal direction and in the verticaldirection being bonded with a resin material. Desirably, the warp 41′has a tensile strength of from 250 to 400 kgf/mm², a tensile modulus offrom 5000 to 18000 kgf/mm², an elongation at breakage of from 2 to 6%,and a tensile toughness of from 500 to 2200 kgf %/mm². Desirably, theweft 42′ has a tensile strength of from 60 to 250 kgf/mm², a tensilemodulus of from 300 to 4500 kgf/mm², an elongation at breakage of from 3to 30% and a tensile toughness of from 300 to 3000 kgf %/mm².

As a material having such properties, the warps 41′ may comprise theyarns containing 100% by weight of aramid fibers or may comprise blendedyarns containing not less than 50% by weight of aramid fibers like thatof the embodiment of FIG. 2. The wefts 42′ may comprise the yarnscontaining non-aramid fibers of an organic material. If described indetail, the non-aramid fibers can be selected from the group consistingof polyester fibers, vinylon fibers and polyamide fibers. Mostdesirably, the nylon fibers are used.

In the foregoing description, the “transverse direction” is the oneperpendicular to the longitudinal direction of the side surface of theside guard 17. Not being limited thereto only, however, the “transversedirection” according to the present invention may include a biasingdirection deviated from the true vertical direction.

Furthermore, the backing member 22 may be the one formed of afiber-reinforced resin composite material like the covering member 21,or may be a metal plate such as a steel plate in its place. when thebacking member is formed of the fiber-reinforced resin compositematerial, its tensile toughness may be smaller than that of the coveringmember 21.

In FIG. 1, the reinforcing member 20 has a U-shape in transverse crosssection. Not being limited to this shape only, however, the reinforcingmember 20 may have any shape provided it is capable of dispersing thestress that is concentrated when the PC steel member 12 collidestherewith by breaking through the side guard 17.

Next, described below is the action of the reinforcing member.

The PC steel member 12 that is broken breaks through the side guard 17made of a concrete or a mortar, comes into collision with the backingmember 22 of the reinforcing member 20 peeling the backing member 22 offthe side surface 17 a of the side guard 17 and stretching and deformingthe covering member 21. At this moment, the backing member 22 absorbsthe kinetic energy of the PC steel member 12 as it peels off the sidesurface 17 a of the side guard 17.

The warps 41 of aramid fibers have a relatively large tensile modulusand absorb the kinetic energy of the broken PC steel member 12 as it ispeeled off the side surface 17 a of the side guard 17. On the otherhand, the wefts 42 have a tensile modulus smaller than that of the warps41 and undergo stretching without being peeled off so much and, hence,absorb the kinetic energy of the PC steel member 12.

As described above, the reinforcing member 20 has energy-absorbingmechanisms that work in quite different ways in the two differentdirections. As a result of compounding these mechanisms, the reinforcingmember 20 is peeled off the side surface 17 a of the side guard 17 in aflat elliptic shape 300, as shown in FIG. 2 having a long diameter inthe longitudinal direction of the side surface 17 a . Therefore, thereinforcing member 20 is not entirely peeled off, the PC steel member 12does not protrude by breaking through the reinforcing member 20, and thePC steel member 12 that is broken is effectively prevented fromprotruding.

The reinforcing member 20 may be obtained in the form of afiber-reinforced resin composite material by curing the woven fabricwith a resin and may then be stuck with an adhesive agent or the wovenfabric may be coated and impregnated with the resin, and may then bestuck simultaneously with the adhesion of the fiber-reinforced resincomposite material.

The foregoing description has dealt with the case of a large prestressedconcrete structure formed by fastening and tightening a plurality ofconcrete molded articles by using a plurality of PC steel members thatextend in the transverse direction penetrating therethrough. However,the same actions and effects are also obtained even when a prestressedconcrete structure is formed by using a single concrete molded articlerelying on the post tension method. In this case, the side guards areprovided on both side surfaces of the single concrete molded article asa matter of course.

The reinforcing member 20 may be constituted by the covering member 21and the backing member 22 as described above, but may also beconstituted by the covering member 21 only. In this case, it isrecommended to use the materials having different tensile toughnesses inthe longitudinal direction and in the transverse direction or in thebiasing direction.

EXAMPLE 1

A steel backing member (100 mm wide, 1600 mm long, 3.2 mm thick) wasprovided on the inside of a covering member of a fiber-reinforced resincomposite material obtained by overlapping three pieces of woven fabricsbonded with a resin, and was bonded thereto with an epoxy resin, and wasadhered onto the side surface of the side guard as shown in FIG. 1.

The woven fabrics forming the reinforcing fiber material containTechnology (trade name) fibers as aramid fibers for constituting thewarps (direction “a”) as well as nylon 6,6 fibers as non-aramid fibersfor constituting the wefts (direction “b”).

In the prestressed concrete structure of the constitution shown in FIG.1, the PC steel rod having a diameter of 32 mm and an overall length of10 meters was artificially broken. The PC steel rod that was broken wasprevented from protruding owing to the above-mentioned reinforcingmember.

Table 1 shows properties of the fiber-reinforced resin compositematerial.

TABLE 1 In the direction of In the direction of Technoloa fibers nylon6,6 fibers Tensile strength 244 kgf/mm² 84 kgf/mm² Tensile elongation3.2% 36.6% Tensile modulus 6900 kgf/mm² 280 kgf/mm² Tensile toughness781 kgf %/mm² 3074 kgf %/mm²

Furthermore, the reinforcing fiber material and the starting yarns wereconstituted as described below.

Constitution of the reinforcing fiber material:

a) weaving texture: 2×1 mat weaving

b) weaving density:

Longitudinal: 38 yarns/2.54 cm

Transverse: 15 yarns/2.54 cm

c) Yarns:

Warps (Technola): 1500 de/1000 fil

Twisting: no twisting

Wefts (nylon 6,6): 1890 de/306 fil

Twisting: 60 T/M

Constitution of the starting yarns;

a) Technola:

Denier: 1500 de

Number of filaments: 1000 fil

Strength: 28 g/de

Elongation: 4.6%

Tensile modulus of elasticity: 590 g/de

Specific gravity: 1.39

b) Nylon 6,6:

Denier: 1,890 de

Number of filaments: 306 fil

Strength: 10.3 g/de

Elongation: 21.7%

Tensile modulus of elasticity: 50g/de

Specific gravity: 1.14

EXAMPLE 2

The reinforcing member was formed of a fiber-reinforced resin compositematerial containing two pieces of reinforcing fiber materials butwithout using the steel backing member on the inside. In this case, too,the PC steel rod could be prevented from protruding. Here, the PC steelrod was 32 mm in diameter and 6 meters long. Properties of thefiber-reinforced resin composite material and constitutions of thereinforcing fiber materials and starting yarns, were the same as thoseof the case of Example 1.

EXAMPLE 3

A steel backing member (100 mm wide, 1600 mm long, 3.2 mm thick) wasprovided on the inside of a covering member of a fiber-reinforced resincomposite material obtained by overlapping three pieces of woven fabricsbonded with a resin, and was bonded thereto with an epoxy resin, and wasadhered onto the side surface of the side guard as shown in FIG. 1.

The woven fabrics forming the reinforcing fiber material contain Kevlar49 (trade name) as aramid fibers for constituting the warps (direction“a”) as well as nylon 6,6 fibers as non-aramid fibers for constitutingthe wefts (direction “b”).

In the prestressed concrete structure of the constitution shown in FIG.1, the PC steel rod having a diameter of 32 mm and an overall length of10 meters was artificially broken. The PC steel rod that was broken wasprevented from protruding owing to the above-mentioned reinforcingmember.

Table 2 shows properties of the fiber-reinforced resin compositematerial.

TABLE 2 In the direction of In the direction of Kevlar 49 nylon 6,6fibers Tensile strength 220 kgf/mm² 84 kgf/mm² Tensile elongation 2.4%36.6% Tensile modulus 6900 kgf/mm² 280 kgf/mm² Tensile toughness 528 kgf%/mm² 3074 kgf %/mm²

Furthermore, the reinforcing fiber material and the starting yarns wereconstituted as described below.

Constitution of the reinforcing fiber material:

a) Weaving texture: 2×1 mat weaving

b) Weaving density:

Longitudinal: 38 yarns/2.54 cm

Transverse: 15 yarns/2.54 cm

c) Yarns:

Warps (Kevlar 49): 1450 de/1000 fil

Twisting: no twisting

Wefts (nylon 6,6): 1890 de/306 fil

Twisting: 60 T/M

Constitution of the starting yarns;

a) Kevlar 49:

Denier: 1450 de

Number of filaments: 1000 fil

Strength: 22 g/de

Elongation: 2.6%

Tensile modulus of elasticity: 820 g/de

Specific gravity: 1.45

b) Nylon 6,6:

Denier: 1,890 de

Number of filaments: 306 fil

Strength: 10.3 g/de

Elongation: 21.7%

Tensile modulus of elasticity: 50g/de

Specific gravity: 1.14

EXAMPLE 4

The reinforcing member was formed of a fiber-reinforced resin compositematerial containing two pieces of reinforcing fiber materials butwithout using the steel backing member on the inside. In this case, too,the PC steel rod could be prevented from protruding. Here, the PC steelrod was 32 mm in diameter and 6 meters long. The properties of thefiber-reinforced resin composite material and constitutions of thereinforcing fiber materials and starting yarns, were the same as thoseof the case of Example 3.

The foregoing examples have dealt with the case where the presentinvention was adapted to the ground cover or the side guard on the sidesurface of a long concrete molded article having a T-shape in crosssection. Not being limited thereto only, however, the present inventioncan be also adapted to the cases where the reinforcing member is stuckto the surfaces having relatively large aspect ratios.

According to the present invention as will be obvious from the foregoingdescription, when the tensile member that is broken projects in theaxial direction and comes into collision with the reinforcing member,the aramid fibers absorb the kinetic energy of the broken tensile memberas they peel off the side surface of the prestressed concrete structure,since they have a relatively large tensile modulus and stretch little.On the other hand, the non-aramid fibers absorb the kinetic energy ofthe broken tensile member as they stretch instead of being peeled off,since they have a smaller tensile modulus than the aramid fibers andeasily stretch.

According to the present invention, the energy absorbing mechanismswhich are different in the two directions are compounded. As a result,the reinforcing member peels off the side surface of the prestressedconcrete structure in a flat elliptic shape having a long diameter inthe longitudinal direction of the side surface. Accordingly, the peelingof the reinforcing member does not reach the side surfaces of theprestressed concrete structure or, if described in further detail, doesnot reach the upper and lower edges of the side surface of the sideguard. Therefore, performance for absorbing the kinetic energy of thebroken tensile member does not decrease. Hence, the broken tensilemember does not protrude by breaking through the reinforcing member andis very effectively prevented from protruding.

Besides, the reinforcing member is integrally formed by thefiber-reinforced resin composite material and is easy to handle, and canbe easily attached to the prestressed concrete structure or to the sideguard thereof on the site.

What is claimed is:
 1. A prestressed concrete structure comprising: anelongated concrete molded article having a pair of side surfaces opposedto each other; a plurality of tensile members laterally extendingthrough the concrete molded article to be secured at each end to theside surfaces of said concrete molded article in a tensioned state, andimparting a compressive load to said concrete molded article; a pair ofside guards arranged along both side surfaces of said concrete moldedarticle so as to cover the ends of said tensile members; and reinforcingmembers arranged on side surfaces of said pair of side guards in orderto prevent broken tensile members from protruding beyond the sidesurfaces of said pair of side guards by breaking through said sideguards when said tensile members in the tensioned state are broken;wherein said reinforcing members stretch little in the longitudinaldirection of the side surfaces of the side guards but easily stretch inthe transverse direction on the side surfaces of said side guards, andwhen pushed from the inside by the ends of the tensile members thatprotrude as a result of breakage, the peeling of said reinforcingmembers easily spreads out in the longitudinal direction of the sidesurfaces of the side guards but spreads out little in the transversedirection on the side surfaces of the said side guards.
 2. A prestressedconcrete structure according to claim 1, wherein said reinforcing memberincludes warps that extend in the longitudinal direction on the sidesurfaces of said side guards, wefts that extend in the transversedirection, and a resin material for bonding said warps and said wefts,said warps having a tensile modulus of from 5000 to 18000 kgf/mm².
 3. Aprestressed concrete structure according to claim 2, wherein said warpshave a tensile toughness of from 500 to 2200 kgf %/mm² and said weftshave a tensile toughness of from 300 to 3000 kgf %/mm².
 4. A prestressedconcrete structure according to claim 2, wherein said warps have atensile strength of from 250 to 400 kgf/mm² and said wefts have atensile strength of from 60 to 250 kgf/mm².
 5. A prestressed concretestructure according to claim 3, wherein said warps contain aramidfibers, and said wefts contain non-aramid fibers.
 6. A prestressedconcrete structure according to claim 5, wherein said wefts are selectedfrom the group consisting of polyester fibers, vinylon fibers andpolyamide fibers.
 7. A prestressed concrete structure according to claim1, wherein said reinforcing member comprises a fiber-reinforced resincomposite material using aramid fibers and non-aramid fibers, andincludes a woven fabric having the following properties A and B:property A: tensile modulus of from 150 to 15000 kgf/mm², property B:tensile toughness of from 400 to 4000 kgf %/mm².
 8. A prestressedconcrete structure according to claim 7, wherein said woven fabriccontains the warps oriented in the longitudinal direction of saidconcrete molded article and the wefts oriented in the transversedirection, the warps using yarns containing not less than 50% by weightof aramid fibers and the wefts using the yarns containing non-aramidfibers.
 9. A prestressed concrete structure according to claim 8,wherein said wefts are selected from the group consisting of polyesterfibers, vinylon fibers and polyamide fibers.
 10. A prestressed concretestructure according to claim 1, wherein said reinforcing membercomprises a fiber-reinforced resin composite material using aramidfibers and non-aramid fibers, and includes a woven fabric having atensile modulus of from 3000 to 15000 kgf/mm² in the direction of aramidfibers and a tensile modulus of from 150 to 3000 kgf/mm² in thedirection of non-aramid fibers.
 11. A prestressed concrete structureaccording to claim 10, wherein said woven fabric has a tensile toughnessof from 500 to 2000 kgf %/mm² in the direction of aramid fibers, and atensile toughness of from 400 to 4000 kgf %/mm² in the direction ofnon-aramid fibers.
 12. A prestressed concrete structure according toclaim 11, wherein said woven fabric has a tensile strength of from 200to 350 kgf/mm² in the direction of aramid fibers, and a tensile strengthof from 50 to 150 kgf/mm² in the direction of non-aramid fibers.
 13. Aprestressed concrete structure according to claim 10, wherein said wovenfabric contains the warps oriented in the longitudinal direction of saidconcrete molded article and the wefts oriented in the transversedirection, the warps using the yarn containing not less than 50% byweight of aramid fibers and the wefts using the yarns containingnon-aramid fibers.
 14. A prestressed concrete structure according toclaim 13, wherein said wefts are selected from the group consisting ofpolyester fibers, vinylon fibers and polyamide fibers.
 15. A prestressedconcrete structure according to claim 2, wherein said reinforcing memberfurther includes a backing member arranged between the side surface ofsaid side guard and the inner surface of said reinforcing member.
 16. Aprestressed concrete structure according to claim 15, wherein saidbacking member is a metal plate.
 17. A fiber-reinforced resin compositematerial comprising a woven fabric of aramid fibers and non-aramidfibers, and a resin for bonding said woven fabric, said woven fabrichaving a tensile modulus of from 3000 to 15000 kgf/mm² in the directionof aramid fibers and a tensile modulus of from 150 to 3000 kgf/mm² inthe direction of non-aramid fibers.
 18. A fiber-reinforced resincomposite material according to claim 17, wherein said woven fabric hasa tensile toughness of from 500 to 2000 kgf %/mm² in the direction ofaramid fibers, and a tensile toughness of from 400 to 4000 kgf %/mm² inthe direction of non-aramid fibers.
 19. A fiber-reinforced resincomposite material according to claim 18, wherein said woven fabric hasa tensile strength of from 200 to 350 kgf/mm² in the direction of aramidfibers, and a tensile strength of from 50 to 150 kgf/mm² in thedirection of non-aramid fibers.
 20. A fiber-reinforced resin compositematerial according to claim 17, wherein said woven fabric uses yarnscontaining not less than 50% by weight of aramid fibers as the warps anduses yarns containing non-aramid fibers as the wefts.
 21. Afiber-reinforced resin composite material according to claim 20, whereinsaid wefts are selected from the group consisting of polyester fibers,vinylon fibers and polyamide fibers.
 22. A sheet member containing awoven fabric of aramid fibers and non-aramid fibers, said woven fabrichaving a tensile modulus of from 3000 to 15000 kgf/mm² in the directionof aramid fibers and a tensile modulus of from 150 to 3000 kgf/mm² inthe direction of non-aramid fibers.
 23. A sheet member according toclaim 22, wherein said woven fabric has a tensile toughness of from 500to 2000 kgf %/mm² in the direction of aramid fibers, and a tensiletoughness of from 400 to 4000 kgf %/mm² in the direction of non-aramidfibers.
 24. A sheet member according to claim 23, wherein said wovenfabric has a tensile strength of from 200 to 350 kgf/mm² in thedirection of aramid fibers, and a tensile strength of from 50 to 150kgf/mm² in the direction of non-aramid fibers.
 25. A sheet memberaccording to claim 22, wherein said woven fabric uses yarns containingnot less than 50% by weight of aramid fibers as the warps and uses yarnscontaining non-aramid fibers as the wefts.
 26. A sheet member accordingto claim 25, wherein said wefts are selected from the group consistingof polyester fibers, vinylon fibers and polyamide fibers.
 27. Aprestressed concrete structure according to claim 7, wherein saidreinforcing member further includes a backing member arranged betweenthe side surface of said side guard and the inner surface of saidreinforcing member.
 28. A prestressed concrete structure according toclaim 27, wherein said backing member is a metal plate.
 29. Aprestressed concrete structure according to claim 10, wherein saidreinforcing member further includes a backing member arranged betweenthe side surface of said side guard and the inner surface of saidreinforcing member.
 30. A prestressed concrete structure according toclaim 29, wherein said backing member is a metal plate.
 31. Aprestressed concrete structure comprising: a plurality of elongatedconcrete molded articles arranged in parallel; a plurality of tensilemembers laterally extending through said plurality of concrete moldedarticles arranged in parallel to be secured at each end to outer sidesurfaces of said concrete molded articles located on outermost sides ofsaid concrete molded article in a tensioned state, and imparting acompressive load to all of said plurality of concrete molded articles; apair of side guards arranged along the outermost sides of the concretemolded articles so as to cover the ends of said tensile members; andreinforcing members arranged on side surfaces of said pair of sideguards in order to prevent broken tensile members from protruding beyondthe side surfaces of said pair of side guards breaking through said sideguards when said tensile members in the tensioned state are broken;wherein said reinforcing members stretch little in the longitudinaldirection of the side surfaces of the side guards but easily stretch inthe transverse direction on the side surfaces of said side guards, andwhen pushed from the inside by the ends of the tensile members thatprotrude as a result of breakage, the peeling of said reinforcingmembers easily spreads out in the longitudinal direction of the sidesurfaces of the side guards but spreads out little in the transversedirection on the side surfaces of said side guards.
 32. A prestressedconcrete structure according to claim 31, wherein said reinforcingmember includes warps that extend in the longitudinal direction on theside surfaces of said side guards, wefts that extend in the transversedirection, and a resin material for bonding said warps and said wefts,said warps having a tensile modulus of from 5000 to 18000 kgf/mm² andsaid wefts having a tensile modulus of from 300 to 4500 kgf/mm².
 33. Aprestressed concrete structure according to claim 32, wherein said warpshave a tensile toughness of from 500 to 2200 kgf %/mm² and said weftshaving a tensile modulus of from 300 to 4500 kgf/mm².
 34. A prestressedconcrete structure according to claim 32, wherein said warps have atensile strength of from 250 to 400 kgf/mm² and said wefts have atensile strength of from 60 to 250 kgf/mm².
 35. A prestressed concretestructure according to claim 33, wherein said warps contain aramidfibers, and said wefts contain non-aramid fibers.
 36. A prestressedconcrete structure according to claim 35, wherein said wefts areselected from the group consisting of polyester fibers, vinylon fibersand polyamide fibers.
 37. A prestressed concrete structure according toclaim 31, wherein said reinforcing member comprises a fiber-reinforcedresin composite material using aramid fibers and non-aramid fibers, andincludes a woven fabric having the following properties A and B:property A: tensile modulus of from 150 to 15000 kgf/mm², property B:tensile toughness of from 400 to 4000 kgf/mm².
 38. A prestressedconcrete structure according to claim 37, wherein said woven fabriccontains the warps oriented in the longitudinal direction of saidconcrete molded article and the wefts oriented in the transversedirection, the warps using yarns containing not less than 50% by weightof aramid fibers and the wefts using yarns containing non-aramid fibers.39. A prestressed concrete structure according to claim 38, wherein saidwefts are selected from the group consisting of polyester fibers,vinylon fibers and polyamide fibers.
 40. A prestressed concretestructure according to claim 31, wherein said reinforcing membercomprises a fiber-reinforced resin composite material using aramidfibers and non-aramid fibers, and includes a woven fabric having atensile modulus of from 3000 to 15000 kgf/mm² in the direction of aramidfibers and a tensile modulus of from 150 to 3000 kgf/mm² in thedirection of non-aramid fibers.
 41. A prestressed concrete structureaccording to claim 40, wherein said woven fabric has a tensile toughnessof from 500 to 2000 kgf%mm² in the direction of aramid fibers, and atensile toughness of from 400 to 4000 kgf %/mm² in the direction ofnon-aramid fibers.
 42. A prestressed concrete structure according toclaim 41, wherein said woven fabric has a tensile strength of from 200to 350 kgf/mm² in the direction of aramid fibers, and a tensile strengthof from 50 to 150 kgf/mm² in the direction of non-aramid fibers.
 43. Aprestressed concrete structure according to claim 40, wherein said wovenfabric contains the warps oriented in the longitudinal direction of saidconcrete molded article and the wefts oriented in the transversedirection, the warps using yarns containing not less than 50% weight byaramid fibers and the wefts using yarns containing non-aramid fibers.44. A prestressed concrete structure according to claim 43, wherein saidwefts are selected from the group consisting of polyester fibers,vinylon fibers and polyamide fibers.
 45. A prestressed concretestructure according to claim 41, wherein said woven fabric contains thewarps oriented in the longitudinal direction of said concrete moldedarticle and the wefts oriented in the transverse direction, the warpsusing yarns containing not less than 50% by weight of aramid fibers andthe wefts using yarns containing non-aramid fibers.
 46. A prestressedconcrete structure according to claim 45, wherein said wefts areselected from the group consisting of polyester fibers, vinylon fibersand polyamide fibers.
 47. A prestressed concrete structure according toclaim 42, wherein said woven fabric contains the warps oriented in thelongitudinal direction of said concrete molded article and the weftsoriented in the transverse direction, the warps using yarns containingnot less than 50% by weight of aramid fibers and the wefts using yarnscontaining non-aramid fibers.
 48. A prestressed concrete structureaccording to claim 47, wherein said wefts are selected from the groupconsisting of polyester fibers, vinylon fibers and polyamide fibers. 49.A prestressed concrete structure according to claim 31, wherein saidreinforcing member further includes a backing member arranged betweenthe side surface of said side guard and an inner surface of saidreinforcing member.
 50. A prestressed concrete structure according toclaim 49, wherein said backing member is a metal plate.